This invention relates to synthetic, nonwoven sheet structures and more particularly relates to a thin, resin-saturable poly(meta-phenylene isophthalamide) paper and a process for making same.
One type of insulation for the windings of electric motors is a laminated structure of polyester film sandwiched between two layers of resin-impregnated, non-woven polyester fabric. In some applications, this material cannot withstand the high temperatures experienced in the windings of the motor. Accordingly, for such applications, it is desirable to use a thermally-resistant sheet or laminate with similar electrical insulating properties.
While known poly(meta-phenylene isophthalamide) papers such as those sold under the trademark NOMEX.RTM. by E. I. du Pont de Nemours & Company are suitable for many electrical applications, they have only a limited degree of resin-saturability. For some applications, a resin-saturable, thermally-resistant insulating paper is desired, e.g., where a smooth surface is desirable in thermally-resistant insulating papers for electric motors. Also, in copying machines, sheets or papers which can absorb silicone oils are needed for use in cleaner rolls. Furthermore, a thin paper of low basis weight which is also resin-saturable is frequently desired for electric motors and other applications.